The present invention relates to a heavy-duty pneumatic tire used for trucks, buses, and the like. Specifically, the present invention relates to a heavy-duty pneumatic tire which suppresses the occurrence of heel-and-toe wear in the shoulder blocks while maintaining the good drainage and traction performance through the final stage of the wear life.
In recent years, heavy-duty pneumatic tires are increasingly used under conditions of high speed oriented running. In a heavy-duty pneumatic tire, putting importance on the traction performance, which includes a number of lug grooves extended in the tire width direction in the tread portion, a problem of heel-and-toe wear occurring in the shoulder blocks has been conspicuous. In particular, in the case that lug grooves with a depth equal to that of the main grooves are provided to the shoulder portion in order to maintain the drainage and traction performance through the final stage of the wear life, the rigidity of the shoulder blocks in the tire circumferential direction is reduced, and the shoulder blocks move to a larger extent while the tire is rolling. Accordingly, it is likely that the heel-and-toe wear occurs.
As means for suppressing the occurrence of such heel-and-toe wear, the following has been proposed and turned into a practice; the suppressing of the movement of the shoulder blocks by providing an elevation, which is lower than the shoulder blocks, to the lug groove between each two adjacent of the shoulder blocks (for example, see Japanese Patent Laid-Open Publication No. 6-297917).
However, the elevation needs to be formed across most part of each lug groove in order to sufficiently suppress the movement of the shoulder blocks. Consequently, significant reduction of the drainage and the traction performance was unavoidable after the middle stage of the wear life.